Yours is an interesting question, but it raises all kinds of issues - not least that some of what you are taking to be fact may not be consistent with reality. I'll mention a few things:
The most important part is that I saw myself living in 41, Gloucester Crescent, Camden Town London. I don't know who lives there now.
The 1939 Register entry for 41 Gloucester Crescent gives names, ages and occupations of the people living there then, and this may have some bearing on what you have been thinking. It can be viewed on the FindMyPast website, but their Terms and Conditions do not allow me to give any details here.
My son at the age of around 5 to 7 years studied in William Ellis school, which was established in 1937 at that location. The year could be around 1937 or after that.
The William Ellis School is a secondary school, which would take pupils from the age of approximately 11 years old.
...I searched on Google earth as I knew by intuition that it was on a road parallel to Regent canal. It was St. Mark's church on Prince Albert road. At that time it barely looked like a church. That tree on the left side of the main gate is now no more.
This is very hard to verify, and of course, we don't know what you saw in your dream. St Mark's was very badly damaged during World War 2, and did not reopen in its current form until 1957. In the meantime, a few parts of the old building and a temporary building in the grounds were used. I haven't been able to find any pictures of either the pre-WW2 church or the temporary buildings for you to compare with what you "saw".
Possibly the biggest problem with this whole question, though, is that in the UK we don't really have the spiritual or philosophical background to know how to handle it. The Judaeo-Christian basis of the British way of life does not incorporate any notion of reincarnation (yes, it teaches that the soul is immortal, but then after death it exists only in a spiritual realm and does not return to another physical body), and although quite a significant number of people say they nevertheless believe in reincarnation, I suspect that it's a kind of wishful thinking for themselves alone, and they haven't really thought through the implications of the reincarnation of others.
You say
I am desperate to meet my children and relatives, if they are somewhere
but I think for most of us, if we were on the receiving end of that, it would be a very unsettling experience. My grandmother died when I was 12, and if a woman about 11 years younger than me were to appear and claim to be her, I would, I think, be rather freaked out, and think that she was suffering some kind of delusion. I don't think I'm unusual in this.
So if you do find any kind of success in your quest, do please bear that in mind. What you believe to be the case may well not be shared by others, and even to make contact runs the risk of hurting and upsetting them, and subsequently rejection for you.
